U.S. flag

An official website of the United States government

Dot gov

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Https

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

PubAg

Main content area

You searched for: Subject "stereochemistry" Remove constraint Subject: "stereochemistry"
Start Over

Search

6,556  Search Results

« Previous | 1 - 20 of 6,556 |
Number of results to display per page

Search Results

1. Copper-Catalyzed Chemo-, Regio-, and Stereoselective Multicomponent 1,2,3-Trifunctionalization of Internal Alkynes

Author:
Weilin Wang; Youliang Wang
Source:
Organic letters 2022 v.24 no.9 pp. 1871-1875
ISSN:
1523-7052
Subject:
stereochemistry,   etc   ; alkynes; stereoselectivity;     Show all 3 Subjects
Abstract:
... Herein, we report the first diaryliodonium salts promoted multicomponent 1,2,3-trifunctionalization of alkynes, where both the acetylenic bond and the adjacent nonactivated propargylic C(sp³)–H bond were functionalized synergistically to generate α-arylated enones with high chemo-, regio-, and stereoselectivity. A broad spectrum of diaryliodonium salts and internal alkynes could be utilized in thi ...
DOI:
10.1021/acs.orglett.2c00499

2. Synthesis of syn- and enantioenriched anti-β-amino alcohols by highly diastereoselective borono-Mannich allylation reactions

Author:
Philip J. Chevis; Thanika Promchai; Christopher Richardson; Thunwadee Limtharakul; Stephen G. Pyne
Source:
Chemical communications 2022 v.58 no.13 pp. 2220-2223
ISSN:
1364-548X
Subject:
stereochemistry,   etc   ; allylation; diastereoselectivity;     Show all 3 Subjects
Abstract:
... A highly diastereoselective method for the synthesis of syn-β-amino alcohols and enantioenriched anti-β-amino alcohols has been developed involving α-hydroxyl aldehydes and chiral α-phenylaminoxyaldehydes or α-benzoyloxyaldehydes, respectively in Petasis borono-Mannich allylation reactions. This study broadens the scope and utility of the Petasis reaction to include pinacol allylboronate and highl ...
DOI:
10.1039/d1cc06775c

3. Fused Tricyclic Guanidine Alkaloids: Insights into Their Structure, Synthesis and Bioactivity

Author:
Nur Zahirah Abd Rani; Yean Kee Lee; Sarfraz Ahmad; Ramu Meesala; Iskandar Abdullah
Source:
Marine drugs 2022 v.20 no.9 pp. -
ISSN:
1660-3397
Subject:
stereochemistry,   etc   ; bioactive properties; guanidines;     Show all 3 Subjects
Abstract:
... A marine natural product possesses a diverse and unique scaffold that contributes to a vast array of bioactivities. Tricyclic guanidine alkaloids are a type of scaffold found only in marine natural products. These rare skeletons exhibit a wide range of biological applications, but their synthetic approaches are still limited. Various stereochemical assignments of the compounds remain unresolved. B ...
DOI:
10.3390/md20090579

4. Potassium-Base-Mediated Autoxidative Diastereoselective Homocoupling of N-Acyl-2-aminoacetophenones

Author:
Yingwei Wang; Mingrong Yang; Chichou Lao; Zhihong Jiang
Source:
Organic letters 2022 v.24 no.14 pp. 2625-2629
ISSN:
1523-7052
Subject:
stereochemistry,   etc   ; autoxidation; dehydrogenation; diastereoselectivity;     Show all 4 Subjects
Abstract:
... We herein report a general and highly efficient method for the synthesis of dl-2,3-diamide-1,4-diones via autoxidative dehydrogenative homocoupling of N-acyl-2-aminoacetophenones mediated by t-BuOK. The transformation is mild, operationally simple, and environmentally friendly. Control experiments and stereochemical results suggest that the substrate undergoes autoxidation followed by a diastereos ...
DOI:
10.1021/acs.orglett.2c00618

5. Stereochemical dominance in hierarchically formed helicates

Author:
Marcel Schlottmann; Tobias Krückel; Markus Albrecht
Source:
Chemical communications 2022 v.58 no.41 pp. 6104-6107
ISSN:
1364-548X
Subject:
stereochemistry,   etc   ; chemical communication; ligands;     Show all 3 Subjects
Abstract:
... The competition of different chiral ligands in the control of stereochemistry of hierarchically formed helical coordination compounds is investigated. It is found that sterically demanding chiral units can dominate the chiral induction of the helix even if they are present as a minor species. Hereby the relative strength of stereoinduction of different chiral units can be evaluated. ...
DOI:
10.1039/d2cc01411d

6. Bottom-Up Approach to Understand Chirality Transfer across Scales in Cellulose Assemblies

Author:
Giulio Fittolani; Denisa Vargová; Peter H. Seeberger; Yu Ogawa; Martina Delbianco
Source:
Journal of the American Chemical Society 2022 v.144 no.27 pp. 12469-12475
ISSN:
1520-5126
Subject:
stereochemistry,   etc   ; cellulose; optical isomerism;     Show all 3 Subjects
Abstract:
... Cellulose is a polysaccharide that displays chirality across different scales, from the molecular to the supramolecular level. This feature has been exploited to generate chiral materials. To date, the mechanism of chirality transfer from the molecular level to higher-order assemblies has remained elusive, partially due to the heterogeneity of cellulose samples obtained via top-down approaches. He ...
DOI:
10.1021/jacs.2c04522

7. Stereoselective Total Syntheses of C18-Oxo Eburnamine-Vincamine Alkaloids

Author:
Wen Zhang; Zhenzhen Wang; Guodan Lin; Yansong Xue; Mengjuan Wu; Pei Tang; Fener Chen
Source:
Organic letters 2022 v.24 no.12 pp. 2409-2413
ISSN:
1523-7052
Subject:
stereochemistry,   etc   ; chemical structure; hydrogenation; stereoselectivity;     Show all 4 Subjects
Abstract:
... Here, we disclose the divergent total syntheses of representative C18-oxo eburnamine-vincamine alkaloids (+)-eburnaminol, (−)-larutenine, and (−)-cuanzine. Key to the approach is a substrate-controlled iridium-catalyzed asymmetric hydrogenation/lactamization cascade that leads to the formation of the common tetracyclic skeleton with essential cis-C20/C21 stereochemistry (93% yield, 98% ee, >20:1 d ...
DOI:
10.1021/acs.orglett.2c00661

8. Theoretical study of a derivative of chlorophosphine with aliphatic and aromatic Grignard reagents: SN2@P or the novel SN2@Cl followed by SN2@C?

Author:
Nandini Savoo; Lydia Rhyman; Ponnadurai Ramasami
Source:
RSC advances 2022 v.12 no.15 pp. 9130-9138
ISSN:
2046-2069
Subject:
stereochemistry,   etc   ; Grignard reagents; Lewis bases;     Show all 3 Subjects
Abstract:
... The proposed SN2 reactions of a hindered organophosphorus reactant with aliphatic and aromatic nucleophiles [Ye et al., Org. Lett., 2017, 19, 5384–5387] were studied theoretically in order to explain the observed stereochemistry of the products. Our computations (using B3LYP as the functional) indicate that the reaction with the aliphatic nucleophile occurs through a backside SN2@P pathway while t ...
DOI:
10.1039/d2ra00258b

9. A Highly Stereospecific Claisen–Sakurai Approach to Densely Functionalized Cyclopentenols

Author:
Ksenia S. Stankevich; Matthew J. Cook
Source:
Journal of organic chemistry 2022 v.87 no.18 pp. 12250-12256
ISSN:
1520-6904
Subject:
stereochemistry,   etc   ; organic chemistry; stereoselectivity; stereospecificity;     Show all 4 Subjects
Abstract:
... The formation of highly substituted cyclopentenols was developed using a Claisen–Sakurai reaction. Both elements of the reaction can be performed in a one-pot sequence that provides the corresponding cyclized products in high stereoselectivity. The stereochemical outcome is defined by a combination of Claisen stereospecificity and stereoelectronic effects in the Sakurai cyclization that promotes r ...
DOI:
10.1021/acs.joc.2c01397

10. Ergostane triterpenoids from the cultures of basidiomycete Favolaschia calocera BCC 36684 and stereochemical elucidation of favolon

Author:
Somporn Palasarn; Kamolphan Intereya; Thitiya Boonpratuang; Chawanee Thongpanchang; Masahiko Isaka
Source:
Phytochemistry letters 2022 v.47 pp. 168-173
ISSN:
1874-3900
Subject:
stereochemistry,   etc   ; Favolaschia; plant biochemistry; triterpenoids;     Show all 4 Subjects
Abstract:
... A bis-epoxide ergostane triterpenoid (favolon), its undescribed derivative (favolon C), and a biogenetically related norergostane (laschiatrion) were isolated from the cultures of basidiomycete Favolaschia calocera BCC 36684. The stereochemistry of favolon was also determined for the first time. Additionally, we propose the revision of the C-24 configuration of laschiatrion to 24R. ...
DOI:
10.1016/j.phytol.2022.01.002

11. A non-natural biosynthesis pathway toward 2-methylisoborneol

Author:
Binbin Gu; Jeroen S. Dickschat
Source:
Chemical communications 2022 v.58 no.27 pp. 4316-4319
ISSN:
1364-548X
Subject:
stereochemistry,   etc   ; 2-methylisoborneol; biosynthesis; stereoselectivity;     Show all 4 Subjects
Abstract:
... The biosynthesis of 2-methylisoborneol was reconstituted by elongation of dimethylallyl diphosphate (DMAPP) with (S)- and (R)-2-methylisopentenyl diphosphate (2-Me-IPP) using farnesyl diphosphate synthase (FPPS), followed by terpene cyclisation. The stereochemical course of the FPPS reaction was studied in detail using stereoselectively deuterated 2-Me-IPP isotopomers. ...
DOI:
10.1039/d2cc00636g

12. Controlled Living Cascade Polymerization of Polycyclic Enyne Monomers: Leveraging Complete Degradability for a Stereochemical and Structural Investigation

Author:
Antonio Rizzo; Eunsong Jung; Hojoon Song; Yunhyeong Cho; Gregory I. Peterson; Tae-Lim Choi
Source:
Journal of the American Chemical Society 2022 v.144 no.34 pp. 15643-15652
ISSN:
1520-5126
Subject:
stereochemistry,   etc   ; alkenes; alkynes; composite polymers; polymerization;     Show all 5 Subjects
Abstract:
... Cascade polymerizations recently gained significant attention due to their use of unique transformations, involving multiple bond making and/or breaking steps, when converting monomers to repeat units. However, designing complex cascade polymerizations which proceed in a controlled manner is very challenging. Various side reactions can hamper polymerization performance and the efficiency of the ca ...
DOI:
10.1021/jacs.2c05721

13. Photochemical Dearomative Cycloadditions of Quinolines and Alkenes: Scope and Mechanism Studies

Author:
Renyu Guo; Souvik Adak; Peter Bellotti; Xinfeng Gao; W. Walker Smith; Sam Ngan Le; Jiajia Ma; K. N. Houk; Frank Glorius; Shuming Chen; M. Kevin Brown
Source:
Journal of the American Chemical Society 2022 v.144 no.38 pp. 17680-17691
ISSN:
1520-5126
Subject:
stereochemistry,   etc   ; alkenes; cycloaddition reactions; photochemistry; quinolines;     Show all 5 Subjects
Abstract:
... Photochemical dearomative cycloaddition has emerged as a useful strategy to rapidly generate molecular complexity. Within this context, stereo- and regiocontrolled intermolecular para-cycloadditions are rare. Herein, a method to achieve photochemical cycloaddition of quinolines and alkenes is shown. Emphasis is placed on generating sterically congested products and reaction of highly substituted a ...
DOI:
10.1021/jacs.2c07726

14. A synthesis-enabled relative configurational assignment of the C31–C46 region of hemicalide

Author:
Tegan P. Stockdale; Nelson Y. S. Lam; Ian Paterson
Source:
Chemical communications 2022 v.58 no.38 pp. 5729-5732
ISSN:
1364-548X
Subject:
stereochemistry,   etc   ; cytotoxicity; diastereomers; polyketides; spectral analysis;     Show all 5 Subjects
Abstract:
... With 21 unknown stereocentres embedded in spatially separated stereoclusters, the cytotoxic polyketide hemicalide represents a seemingly intractible structural assignment problem. Herein, through the targeted synthesis of configurationally defined fragments, as well as “encoded” mixtures of diastereomers, the stereochemical elucidation of the C31–C46 region of hemicalide is achieved. Detailed NMR ...
DOI:
10.1039/d2cc01802k

15. Asymmetric total synthesis of prostaglandin C₂ TBS ether

Author:
Xiaofen Yi; Xueyu Long; Yu Chen; Xiangling Cen; Pei Tang; Fener Chen
Source:
Chemical communications 2022 v.58 no.40 pp. 6000-6003
ISSN:
1364-548X
Subject:
stereochemistry,   etc   ; chemical communication; ethers; prostaglandins; stereoselective synthesis;     Show all 5 Subjects
Abstract:
... We disclose an asymmetric total synthesis of prostaglandin C₂ TBS ether, a derivative of an extremely sensitive natural prostaglandin C₂. The key to the synthesis is a SmI₂-mediated ketyl–enoate reaction that leads to the formation of the functionalized cyclopentane ring with high-level stereochemical control. Access to the crucial alkene system is realized late in the synthesis by the implementat ...
DOI:
10.1039/d2cc01737g

16. Kinetic Resolution of 2-Aryl-4-methylenepiperidines toward Enantioenriched Functionalizable Piperidine Fragments

Author:
Anthony Choi; Anthony J. H. M. Meijer; Ilaria Proietti Silvestri; Iain Coldham
Source:
Journal of organic chemistry 2022 v.87 no.13 pp. 8819-8823
ISSN:
1520-6904
Subject:
stereochemistry,   etc   ; drugs; organic chemistry; piperidines; sparteine; spectroscopy;     Show all 6 Subjects
Abstract:
... The base n-BuLi with sparteine allows a kinetic resolution of N-Boc-2-aryl-4-methylenepiperidines. The 2,2-disubstituted products and recovered starting materials were isolated with high enantiomeric ratios. From VT-NMR spectroscopy and DFT studies, the rate of rotation of the N-Boc group is fast. Lithiation and trapping of the enantioenriched starting materials gave 2,2-disubstituted piperidines ...
DOI:
10.1021/acs.joc.2c00862

17. 17,20-Epoxysteroids from octocoral Isis hippuris (Linnaeus, 1758)

Author:
Yi-Qi Huang; Po-Jen Chen; San-Nan Yang; Su-Ying Chien; Li-Guo Zheng; Zhi-Hong Wen; Liang-Mou Kuo; Ping-Jyun Sung
Source:
Tetrahedron letters 2022 v.108 pp. 154142
ISSN:
0040-4039
Subject:
stereochemistry,   etc   ; X-ray diffraction; cytotoxicity; metabolites; Taiwan;     Show all 5 Subjects
Abstract:
... Three 17,20-epoxysteroids, including a new metabolite, hippuristeroketal B (1), as well as two known compounds, hippuristerones A (2) and I (3), have been isolated from octocoral Isis hippuris collected off the waters of Taiwan. The structure of steroid 1 was deduced by extensive 1D and 2D NMR studies. The absolute stereochemistry of steroids 1–3 was determined by single-crystal X-ray diffraction ...
DOI:
10.1016/j.tetlet.2022.154142

18. Catalytic Enantioselective α-Alkylation of Amides by Unactivated Alkyl Electrophiles

Author:
Xiaoyu Tong; Felix Schneck; Gregory C. Fu
Source:
Journal of the American Chemical Society 2022 v.144 no.32 pp. 14856-14863
ISSN:
1520-5126
Subject:
stereochemistry,   etc   ; Lewis acids; amides; catalysts; enantioselectivity; nickel;     Show all 6 Subjects
Abstract:
... Carbonyl groups that bear an α stereocenter are commonly found in bioactive compounds, and intense effort has therefore been dedicated to the pursuit of stereoselective methods for constructing this motif. While the chiral auxiliary-enabled coupling of enolates with alkyl electrophiles represented groundbreaking progress in addressing this challenge, the next advance in the evolution of this enola ...
DOI:
10.1021/jacs.2c06154

19. Synthesis of Pleuromutilin

Author:
Nicholas J. Foy; Sergey V. Pronin
Source:
Journal of the American Chemical Society 2022 v.144 no.23 pp. 10174-10179
ISSN:
1520-5126
Subject:
stereochemistry,   etc   ; bacterial proteins; cycloaddition reactions; protein synthesis;     Show all 4 Subjects
Abstract:
... Synthesis of a potent inhibitor of bacterial protein synthesis, pleuromutilin, is described. Assembly of the critical cyclooctane fragment relies on an oxidative ring-expansion, and complete stereochemical relay in the synthetic sequence is enabled by the judicious choice of tactics. The requisite connectivity pattern of the perhydroindanone motif is rapidly established in a sequence of cycloaddit ...
DOI:
10.1021/jacs.2c04708

20. Asymmetric Total Synthesis of (+)-Alstonlarsine A

Author:
Jun-Jun Yao; Rui Ding; Xiaoming Chen; Hongbin Zhai
Source:
Journal of the American Chemical Society 2022 v.144 no.31 pp. 14396-14402
ISSN:
1520-5126
Subject:
stereochemistry,   etc   ; alkylation; carbonates; cycloaddition reactions; indoles; ligands;     Show all 6 Subjects
Abstract:
... The first asymmetric total synthesis of (+)-alstonlarsine A has been realized. The prominent features of the current synthesis include the following: (i) a Pd/self-adaptable ligand complex-catalyzed asymmetric allylic alkylation of 2-methyl-2-cyclopentenyl carbonate with 2-indolylsubstituted dimethyl malonate to establish the key stereocenter of C15, (ii) an intramolecular nitrile oxide-alkene [3 ...
DOI:
10.1021/jacs.2c06518